API工具类

工具类

		java.lang
			|--包装类
			|--String类
			|--StringBuffer类
			|--Object类
			|--Class类
			
		java.util
			|--Date类
			|--集合类
			|--Properties
		java.io
			|--File类
			|--InputStream / OutputStream
							|--FileInputStream/FileOutputStream
							|--BufferedInputStream/BufferedOutputStream
			|--Reader/Writer
							|--FileReader/FileWriter				
							|--BufferedReader/BufferedWriter
			|--InputStreamReader/OutputStreamWriter
			
		java.awt/javax.swing
				|--GUI